(.module:
  [library
   [lux (#- Type)
    [abstract
     [equivalence (#+ Equivalence)]
     [order (#+ Order)]
     [hash (#+ Hash)]]
    [data
     ["." product]
     ["." text ("#\." order)
      ["%" format (#+ format)]]]]]
  ["." // #_
   ["#" artifact (#+ Artifact) ("#\." order)
    [type (#+ Type)]]])

(type: .public Dependency
  (Record
   {#artifact Artifact
    #type Type}))

(def: .public hash
  (Hash Dependency)
  ($_ product.hash
      //.hash
      text.hash
      ))

(def: .public equivalence
  (Equivalence Dependency)
  (\ hash &equivalence))

(implementation: .public order
  (Order Dependency)

  (def: &equivalence
    ..equivalence)

  (def: (< reference subject)
    (<| (or (//\< (value@ #artifact reference)
                  (value@ #artifact subject)))
        
        (and (//\= (value@ #artifact reference)
                   (value@ #artifact subject)))
        (text\< (value@ #type reference)
                (value@ #type subject)))))